Technical Field
The present disclosure is directed to a method of preparing a metal/carbon nanocomposite and nanocomposite thin films made by the method, the use of the nanocomposite films as plasmonic photocatalysts, in SERS-based sensors, as biomedical coatings, and for antimicrobial applications such as water remediation. More specifically, the disclosure is directed to an excimer laser irradiation process for the preparation of textured Ag/C nanocomposite thin films.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Nanomaterials, such as nanocomposites, are multiphase solid materials wherein one of the phases has one, two or three dimensions of less than 100 nanometers (nm), or structures having nano-scale repeat distances between the different phases that make up the material. The properties of nanocomposites are determined not only by the morphology and spatial distribution of the nanophase, but also depend on mutual chemical and physical interactions between the various phases involved. Furthermore, a nanocomposite is any composite material, one or more, of whose components are some form of nanoparticle. Nanoparticles, by definition, are particles between 1 nm and 100 nm in size. In nanotechnology, a particle is defined as a small object that behaves as a whole unit with respect to its transport and properties.
Metal nanoparticles, in particular, are recognized as being important contributors to the fields of chemistry, physics and biology due to their unique optical, electrical and photo-thermal properties. Such metallic nanoparticles have great potential for application in laboratory settings, as they can be used as probes in mass spectroscopy, and can also be employed in the colorimetric detection of proteins and DNA molecules. Metal nanoparticles have furthermore been used for therapeutic applications and drug delivery. One metal of great interest is silver, in both nanoparticle and nanocomposite form.
Silver nanoparticle-based materials have recently gained great interest due to their potential for use in a variety of fields, such as selective heterogeneous catalysis. Heterogeneous catalysis, in chemistry, refers to the form of catalysis where the phase of the catalyst differs from that of the reactants. This can include catalysis reactions such as hydrogenation, [B. J. Li, H. B. Li, Z. Xu, Experimental evidence for the interface interaction in Ag/C60 nanocomposite catalyst and its crucial influence on catalytic performance. J. Phys. Chem. C 11 (2009) 21526-21530 Incorporated by reference herein in its entirety], oxidation, [S. Y. Wu, Y. S. Ding, X. M. Zhang, H. O. Tang, L. Chen, B. X. Li. Structure and morphology controllable synthesis of Ag/carbon hybrid with ionic liquid as soft-template and their catalytic properties. J. Solid State Chem. 2008, 181 (2008) 2171-2177. Incorporated by reference herein in its entirety], and hydrogen storage [S. Rather, M. Naik, S. W. Hwang, A. R. Kim, K. S. Nahm. Room temperature hydrogen uptake of carbon nanotubes promoted by silver metal catalyst. J. Alloy Compd. 475 (2009) L17-L21 Incorporated herein by reference in its entirety].
Additionally, for many applications, the use of spherical nanoparticles is desired. Methods are needed for consistent production of spherical metal nanoparticles for incorporation into nanocomposites. Moreover, there is also need for the development of cubic nanoparticles as well. Cubic nanoparticles, such as those incorporated into gold and silver nanocomposites, can be used to amplify the difference in left- and right-handed molecules' response to circularly polarized light. Several studies have indicate that these cubic nanoparticles provide the basis for probing the effects of chirality, or handedness, in molecular interactions with increased sensitivity over prior methods [Fang Lu, Ye Tian, Mingzhao Liu, Dong Su, Hui Zhang, Alexander O. Govorov, Oleg Gang, Discrete Nanocubes as Plasmonic Reporters of Molecular Chirality Nano Lett., 2013, 13 (7), pp 3145-3151DOI: 10.1021/n1401107g Publication Date (Web): Jun. 18, 2013 American Chemical Society, Incorporated herein by reference in its entirety]. There is a need for rapid methods of synthesizing both spherical and cubic silver nanoparticles, given their wide range of applications.
In addition to gold/silver nanocomposites, silver nanoparticle-based materials can incorporate other components, such as carbon, to form a nanocomposite indicated by Ag/C which signifies a core/shell structure, in which Ag is the core and C forms the shell. Herein “/” indicates a core/shell form. In such form, Silver/Carbon nanocomposites have a wide array of applications, including catalysis.
Metal nanoparticles have proven effective as plasmonic photocatalysts due to their surface plasmon resonance effects. Surface plasmon resonance (SPR) relates to the enhanced reflectivity of a dielectric material. Recently, due to the SPR effect of silver nanoparticles, silver/carbon nanocomposites were reported as efficient plasmonic photocatalysts due to their enhanced reflectivity under visible light [S. M. Sun, W. Z. Wang, L. Zhang, M. Shang, L. Wang. Ag/C core/shell nanocomposite as a highly efficient plasmonic photocatalyst. Catal. Commun. 11 (2009) 290-293. Incorporated herein by reference in its entirety]. Additionally, Ag/C nanocomposites have exhibited high photocatalytic activity in the decomposition of aqueous and gaseous compounds under visible-light irradiation. The origin of this high photocatalytic activity is mainly ascribed to the surface plasmon resonance (SPR) effect of silver nanoparticles in the Ag/C composite. Thus, these Ag/C nanocomposites are considered to be promising materials for use in solar light harvesting devices and sensors due to their photocatalytic activitiy.
In addition to the above applications, Ag/C nanostructures are important for biological applications due to the surface functional groups provided by the carbonaceous products [S. Li, X. Yan, Z. Yang, Y. Yang, X. Liu, J. Zou. Preparation and antibacterial property of silver decorated carbon microspheres. Appl. Surf Sci. 292 (2014) 480-487. Y. Zhao, Z. Q. Wang, X. Zhao, W. Li, S. X. Liu. Antibacterial action of silver-doped activated carbon prepared by vacuum impregnation. Appl. Surf. Sci. 266 (2013) 67-72. X. M. Sun, Y. D. Li. Ag/C core/shell structured nanoparticles: controlled synthesis, characterization, and assembly. Langmuir 21 (2005) 6019-6024. Incorporated herein by reference in their entirety]. The antibacterial role of the Ag/C nanocomposites is due to the toxicity of silver to microbes, and the use of silver nanoparticles is of interest because of the slower, more controlled release of silver ions. The slower release of silver cations, from silver nanoparticles and/or silver/carbon nanocomposites, can avoid the constant delivery of an excess amount of silver to the area compared with other Ag+ based chemicals. Also, in using silver nanoparticles and nanocomposites, the metallic silver is not as susceptible to deactivation by a chloride molecule as compared with silver ions [Dunn, K.; Edwards-Jones, V. The role of Acticoat with nanocrystalline silver in the management of burns; Wythenshawe Hospital Burns Unit, Manchester, UK: England: United Kingdom, 2004; pp S1-9, Incorporated herein by reference in its entirety.]
There is a considerable interest and need for the advancement of preparation techniques for metal nanoparticle, metal/carbon nanocomposites, and specifically, Ag/C nanocomposites, also described as core/shell nanocomposites. The preparation of metal/carbon nanocomposite thin films, such as Ag/C nanocomposite thin films, wherein texture variations result from differences in the molar ratio of carbon to the metal nanoparticle core is of further interest.
The preparation of silver and carbon core/shell composites has been reported by both chemical and photochemical methods [S. M. Sun, W. Z. Wang, L. Zhang, M. Shang, L. Wang. Ag/C core/shell nanocomposite as a highly efficient plasmonic photocatalyst. Catal. Commun. 11 (2009) 290-293., X. M. Sun, Y. D. Li. Ag/C core/shell structured nanoparticles: controlled synthesis, characterization, and assembly. Langmuir 21 (2005) 6019-6024, Incorporated herein by reference in their entirety.] However, these processes have disadvantages, in that they require significantly lengthy production times for synthesis, and the resulting silver particle size distribution is not narrow. Furthermore, prior methods for forming silver carbon nanoparticles utilize surfactants and suffer from issues with agglomeration, low volume production, and impurity.
The use of metal/carbon nanocomposites in the formation of thin films is an additional area of research for which there is considerable interest and need for advancement. Nanocomposite thin films possess improved mechanical, electronic and magnetic properties as a result of several factors, such as crystallite size and textures. These factors depend significantly on the material selection, deposition methods, and process parameters in forming the nanocomposite thin films. Materials for nanocomposite thin films include, but are not limited to metals, such as silver, gold, palladium, nickel, cobalt, and non-metals such as carbon and nitrogen. By definition, thin film composites can include particles, both microparticles and nanoparticles, dispersed therein. Nanocomposite films comprise at least two phases, a nanocrystalline phase and an amorphous phase, or alternatively, a nanocrystalline phase with another nanocrystalline phase [S. Zhang, Y. Fu, H. Du, Y. Liu, T. Chen, Nanocomposite Thin Films for both Mechanical and Functional Applications 2004 dspace.MIT-edu. Incorporated herein by reference in its entirety.] Due to their unique physical-chemical properties, nanocomposite thin films have recently gained interest for use in both the mechanical and functional fields, and furthermore, metal/carbon nanocomposites and nanocomposite thin films have been described as lubricants for solid surfaces.
Techniques for preparation of nanocomposite films include, but are not limited to, magnetron sputtering, chemical vapor deposition, and laser ablation. In considering laser ablation methods, there are many types of lasers that can be employed; each operating at a defined wavelength of light. In view of optical properties, excimer lasers possess advantages over other types of lasers, including the Nd:YAG laser, in thin film manufacturing. The advantages are largely based on their superior ablation characteristics and much better energy stability. Major drawbacks of the Nd:YAG lasers for pulsed laser deposition (PLD) include a Gaussian beam profile instead of a flat-top profile, as well as temperature-induced polarization and thermal lensing effects which can create donut-shaped beam profiles and lateral distortions. [Pulsed laser deposition—UV laser sources and applications R. Delmdahl, R. Pätzel Coherent GmbH, Hans-Böckler-Str. 12, D-37079 Gottingen, Germany PACS 42.55.Lt, 52.38.Mf, 81.15.Gh Incorporated herein by reference in its entirety.]
New preparation methods are sought to overcome disadvantages with the conventional preparation of metal/carbon nanoparticles and metal/carbon nanocomposite thin films. Accordingly, one objective of the present disclosure is to provide methods or processes of preparing nanocomposites and nanocomposite thin films.